The current research emphasis of our laboratory is within the area of immunoregulation and immunological tolerance. The approach taken is from the perspective that the regulation of the immune response is many faceted in that it reflects the multidimensional response which characterizes the immune system. Implicit in this approach is the question as to whether states of adult induced immunological unresponsiveness accurately reflect the biological basis for the process of self-nonself discrimination or whether they are more germane to the understanding of immune homeostasis. Consonant with these aims, we are now performing studies on the cellular basis and inherent mechanisms in neonatally induced tolerance in the light that unresponsiveness induced in the perinatal state may be more biologically relevant to immunological self discrimination. Specific projects which are currently being investigated in the laboratory include 1) the mechanisms of unresponsive states induced in adult animals by heterologous soluble serum proteins and by haptens coupled to isologous globulins, 2) cellular events and mechanisms of neonatally induced unresponsiveness and their relationship to the ontogenetic development of immune responsiveness and immune suppression, 3) studies in the role of the Fc receptor in lymphocyte activation and regulation, 4) antigenic recognition in different functional lymphocyte populations using cytochrome c as an antigenic probe.